Why is there a New Flu Vaccine Every Year?

The flu is a respiratory infection caused by a group of viruses. Symptoms range from mild to severe and most commonly include body aches, cough, fever, headache, and sore throat. The flu is contagious, spreading through tiny droplets from a cough, sneeze or even talking. We hear about it every year in the fall and winter because the viruses tend to survive longer in those seasons. The flu vaccine is created to protect against influenza strains A and B. Once an individual is vaccinated, the body’s immune system responds by developing antibodies that will be ready to combat future infections. It takes about two weeks after a person has been vaccinated to gain protection. It is not unusual to briefly experience mild fatigue and muscle aches soon after injection as this represents an appropriate immune response, but because the ingredients in the flu shot have been inactivated, it is not possible to get “the flu” from the vaccine. The flu vaccine is recommended for most people over six months of age and is given every year because:

The Circulating Flu Viruses Change

Influenza viruses undergo structural antigenic change and even mutation. Each February, flu experts gather and review the data to best decide what strains are predicted to circulate in the Northern Hemisphere during the upcoming flu season. Once the top 3 or 4 strains are identified, the viruses are grown then the vaccines are manufactured using varying methods to create the safest and most effective flu shot. Typically, there is at least one and usually more than one new strain coverage included each year.

Immune Protection Declines Over Time

Over time, the antibodies created in response to that year’s vaccine begin to lose their effectiveness, though some individuals who received annual flu shots over many years maintain reserve immunity capable of preventing or softening the blow of a new infection even if challenged with a novel strain. The CDC recommends a yearly flu shot around October. Another advantage to getting the flu shot is that you are less able to carry and spread the virus to others that may have an altered immune status. Due to the fact older individuals don’t mount as robust of an immune response following vaccination, it is especially important for those over 65 years old to get the vaccine annually. The CDC estimated that in the 2018-2019 flu season, there were approximately 490,600 hospitalizations and 34,200 deaths from the flu. It’s safe to say the flu is a dangerous but preventable illness. We thank all volunteers that have contributed to now FDA-approved and currently enrolling flu vaccine programs. Your participation has helped to save lives. 

Reference:

Centers for Disease Control and Prevention https://pubmed.ncbi.nlm.nih.gov/9360364/ https://www.cdc.gov/flu/prevent/keyfacts.htm https://www.sciencedaily.com/releases/2019/03/190320110619.htm